Denying access to non-authorized users.1. Once the server screen is opened, and you can see the logs, click Edit then Settings at the top.
2. Under "General Settings" find "Ip Filter."
3. Under the first box, put a asterisk. (*)
4. Under the second box, put your IP address.

The first option will defiantly work 100%, while the second will work if the unknown login attempts are unable to be logged in, therefore after so many attempts they will get banned for a period of time.